Abstract

In order to improve the spectral efficiency of coherent optical communication systems, it has recently been proposed to make use of the orthogonal frequency-division multiplexing offset quadrature amplitude modulation (OFDM-OQAM). Multiple optical channels spaced in the frequency domain by the symbol rate can be transmitted orthogonally, even if each channel overlaps significantly in frequency with its two adjacent channels. The solutions proposed until now in the literature unfortunately only address a single polarization communication, and therefore do not benefit from the capacity gain reached when two polarizations are used to transmit independent information signals. The aim of the present paper is to propose a receiver architecture that can decouple the two polarizations. We build an equalizer per channel at twice the symbol rate and optimize it based on the minimum mean square error (MMSE) criterion. We demonstrate the efficiency of the resulting system compared to the Nyquist wavelength-division multiplexing (N-WDM) system both in terms of performance and complexity. We also assess the system sensitivity to transmit synchronization errors and show that system can even work under significant synchronization errors.

Figures (8)

Comparison of performance between the QAM and OQAM-FBMC systems for a varying SNR at the input of the receiver. The symbol rate, channel bandwidth and channel spacing are all equal to 30 Gsymb/s or GHz.

Performance of the OFDM-OQAM system as a function of the equalizer memory length for a varying symbol rate. The channel bandwidth and channel spacing are varying according to the symbol rate. The received SNR is fixed to 20 dB.